Electrical condenser device



May 2, 1933. J. E. LILIENFELD 1,906,691

ELECTRICAL CONDENSER DEVICE Filed March 28, 1928 J a 13 ,Silver W /A Z Copper and j IZ (opper SuahL'de ATTRNEY Patented May 2, 1933 l UNITED STATES "PATENT OFFICE JULIUS EDGAR LILIENFELD, F BROOKLYN, NEW YORK ELECTRICAL CONDENSER DEVICE Application led March 28, 1928. l Serial No. 265,373.

The invention relates to a condenser device indicated, in order to increase the effectivefor use in connection with electric circuits; ness of the insulation, a linal coating of parand it has for its object the provision ot' a ticulai'ly good conducting quality, as of silsimple, compact, substantial and effective Ver, platinum, tin, nickel, aluminum, etc., d

device of this character which4 withal shall however, being generally provided so as to 55 be comparatively inexpensivey to construct; secure a good contact for the outside lead. also, a condenser which shall have extremely These coatings, in particular as Well as in high specific capacityof the order of magcertain instances also the initial coatings, may nitude of 0.02 infds. per cm2., With a total be precipitated from colloidal metal suspenthickness of the inished product which may sions; or they may be metal-sprayed. fio be less than l mm. The dielectric layer or layers when thus If a coating o compounds of a metal, 'ici coated maintain a highly insulating prop example, the oxide of aluminum, iiiagneerty, affording a substantial insulation besium, tantalum, tungsten, etc., be produced tween the underlying metal which represents partly or entirely over a surface of the reone of the condenser plates and the'conduct- 65 spcctive metal selected, or an alloy of several ing coating or coatings Which represents the of these metals, an insulating layer having other plate of the condenser, so that it is high dielectric properties may be attained; possible to apply voltages of the order of and I have discovered that such layers may magnitude of 100 volts across a dielectric '20 be used in a minute thickness as the dielecthus produced and of a thickness of the order 7bA tric of a commercial condenser, provided a 0i' magnitude of only 10*4 min. Without puncfurther layer or coating of substantially turing it. ln fact, the condenser will in many more conductive material be integrally assoinstances possess self-healing properties, In ciated therewith by applying this material an aluminum-aluminum oxide condenser in disintegrated or finely subdivided state, Withan oxidizable conducting layer of cope. g. by spraying or by spattering it in a per, aluminum, magnesium, etc., short cirvacuum cathodically from such metals as cuits will disappear as soon as the condenser copper, lead, aluminum, etc., over' said diis momentarily subjected to a load. This is electric layer. OrV said layer may be applied a possible explanation of the fact, `which I by colloidal precipitation, it being underhave discovered. that the allowable voltage stood that substantially molecular contact appears to be a function not only of the naover the Whole area is had between it and ture and thickness of the dielectric layer but the dielectric layer. Under these circumalso of the physical and chemical properties stances such insulating layers, l also have of the superposed coatings.

discovered, do not possess rectifyiiig prop- A coating produced by spattering from a erties similar to those which ane being shown copper cathode over the dielectric layer, ior

b diierent combinations, for example, When example, imparts to the layer the property of aliiminum oxide is deposited on an aluminum withstanding a higher voltage than silver 40 electrode of an electrplytic cell with ainrnosimilarly applied. rlhe more effective coat- I niuin borate as electrolyte; on the contrary, ings, however, may, in some cases, not be very the layers show insulating properties for highly conductive; and it is, therefore, somevoltages applied in either direction. times desirable to provide more than one coat- The underlying or base material is prefing over the layer, the outer of them to possess 45 erably of relatively thin metal, approximatea particularly good conducting quality; and

ly 0.03 mm. or less, to prevent, in case or the saine may be applied in any suitable manbending, distortion of the saine and injury ner, for example, electrolytically. to the superposed layers. The dielectric layer may readily be at- In some cases it may be advisable to apply tained of said minute thickness by electrolytic more than one coating over the firstI and inor by purely chemical methods, e. g. heat oxisulating layer in succession in the manner datioii, sulfurization, etc., forming the same 10 of and directly on the metal base which vrepresents one ofdthe condenser plates; for

example, a dielectric layer consist' of the oxide of aluminum thus formed direct y of an underlying solid conductin base of aluminum has been found very satisfactory for this purpose. Over this layer is to be provided the superposed coating of substantially greater conductivity than the dielectric, Vand suitable provision is to be made for affording electrical connection on one hand with the base element and on the other hand with the conductin coating located about the intermediate dielectric.

In many cases, very satisfactory results are had with the superposed coating consisting partl or wholly of a compoun of certain meta s; and this may be attained in different ways. For instance, if a metal, e. g. ,co per, electrode is used in sputtering, layers o different natures may be obtained according to f the gas filling of the spattering'container in which the spattering is conducted as well as to the electrical conditions prevailing therein. Thus, either a pure metallic layer, (Cu) layer of a compound (CugO) or, preferably, a mixture of both may be produced directly by the spattering rocess.

On the other han compounds particularly suitable for this purpose may be obtained by subjecting a spattered coating to subsequent chemical treatment. For example, the coating initially deposited may be treated in sulfur vapor or with carbon disulfide in which elemental sulfur is dissolved; or, it may be subjected to oxidation by heat treatment or by oxidizing reagents, e. g. H2O2 etc.; or, it may be treated, as in the case of a coating of lead, in vacuo with atomic oxygen in order to convert it into PbOz.

A very compact and extremely effective condenser is attained in the aforesaid manner, it bein possible to thus construct condensers of integral structure having a constant specific capacity which may be as high as 0.02 mfds. per cm2. more or less, according as the polarizing voltage in the preparation of the underlying or base material was low or high, while the total thickness of the commercial product may be substantially less than one millimeter, depending on the materials used.

In the accompanying drawing which illustrates the invention:

Fig. 1 is a fragmentary longitudinal section illustrating the novel condenser and shown greatly magnified and on a disproportionate scale for purpose of illustration.-

Fig. 2 is a similar view illustrating a modilication. Figs. 3 and 4 are respectively a front elevation and transverse vertical section of a completed condenser unit, but shown greatly magnified and on a disproportionate scale for purpose of illustration.

Figs. 5 and are/similar views illustrating a further embodiment of the condenser, Fig. 5 being a front elevation and Fig. 6 a horikzontal section taken on the line 6 6, Fig. 5.

Referring to the drawing, 10 designates a metal such as aluminum, magnesium, tantalum, tungsten, etc., which forms the base or supporting element of the condenser; and, in accordance with the invention, there is provided over a portion of the surface thereof, or over substantially the entire surface if desired, a non-conducting or insulating layer 11 which is formed as a compound of the particular metal formin the said base member. For example, if auminum be selected as the base member, the insulating layer 11 will be the oxide of aluminum (A1203), which may be rovided thereon in an suitable and wellnown manner as by e ectrolytic or purely chemical methods. If, in the ormer instance, a high volta e condenser is to be formed, it is advisale to employ voltages as high as possible; and when aluminum is utilized as the base material, the voltage in the electrolytic process will range up to 400 volts in an aqueous solution and up to 1,500 volts in an alcoholic solution. This layer then is an integral part of the base material which is selected, also, to be of relatively thin stock-approximating 0.03 mm. or less, so that in case of bending of a completed condenser unit there will be no serious distortion of the said base member and resulting injury to said layer of oxide, as well as to the further coatings hereinafter more full set forth. The dielectric layer itself is to e of minute thickness only, for example, of the order of magnitude of l0 mm., so as to afford the extraordinarily high specific capacities attained when provided with a superposed substantially more conductive coating or coatings integrally associated therewith.

To this end, there is provided over the aforesaid layer of oxide and in a molecular contact with it over the total contact area one or more substantiall more conductive coatings 12 and 13 of disintegrated or finely subdivided metal or metallic compounds, or mixtures of such metal and compound.

'These coatings may also be of extreme thinness, in fact not any thicker than required in order to provide for a ood contact possibility, and are applied in disintegrated or finely subdivided state, as by sputtering cathodically from such metals as copper, lead,

aluminum, etc., the desired coatings. Or, the same may be attained by precipitation from colloidal metal suslpensions or by pressure spraying. A pure y metallic coating or a coating consisting o a metal and compound thereof, or solely a compound, may constitute the layer 12, for example, as a copper and co per oxide mixture.

owever, while such coatings of mixtures or solely com ounds appear to be ca able of increasing substantially the .u per imit of the allowable voltages some o them are not very highly conductive; and it may' be advantageous in particular cases to provide thereover an additional coating 13 of particularly good conducting quality, as well as having nontarnishing properties, for exampleya coating of silver, nickel, aluminium, etc.

Compounds especially suitable yfor the purpose of increasing the puncturing voltage may be obtained by a subsequent treatment of the deposited coating as by treatment in sulfur vapor or with carbon disulfide in which elemental sulfur has lbeen dissolved. Or, a deposited coating may be subjected to oxidation by heat .treatment or by means of oxidizing reagents such as H2O2, etc.; or in vacuo with atomic oxygen as in the case of a coating of lead in order to convert it into Pb02. i In Fig. 2 a condenser thus constituted is indicated, the outer and inal coating 12 overlying the dielectric layer of aluminum oxide consisting of copper sulfide (CugS).

In Figs. 3' and 4, apractical embodiment of the invention has been set forth, the same ycomprising a centrally disposed base elementy 15, as of aluminum, upon which has been provided a layer 16 of aluminum oxide, asaforesaid, the same in this instance substantially covering the entire surface of the base element 15 with the exception of a projecting tongue member 17 thereof. Two further coatings 18 and 19 are applied over the said oxide layer, the under coating consisting of a mixture of copper and copper oxide While the outer'consists of silver.

Contact with the condenser thus afforded may be through a pliable conducting Inaterial such as tin or lead foil 20 which insures a good contact with the outermost coating 19 and affords, also, ready means for outside connection as through a conductor 21 attached thereto. Further contact may be had to the condenser through the tongue 17, as through a conductor 22, thus completing the means for applying voltage to said condenser. Moreover, an insulating cover 23 as of varnish, paper, rubber, etc., is provided over the tongue 17 and portion of the foil 20 to prevent short-circuiting of the condenser elements. The condenser thus constructed may be placed in an air-tight envelope or the like (not shown) and suitably protected in accordance with the usual practice.

While the design of condenser indicated' in Figs. 3 and 4 has been found satisfactory for lower voltages, it is advisable to modify this design somewhat when the condenser is to be utilized in connection with high voltages and more particularly to the extent of avoiding contact of the underlying oxide-coated aluminum base element 15 and the contact-making surrounding foil 20 with.

ycoated as in the previously described embodiment, but the overlying substantially more conductive coating 26 1s applied in a manner to leave a margin of the oxide layer entirely surrounding said coating 26. Over the latter is then arranged a stri of insulating paper 27, or the same may e wrap ed around the base with coating, said paper ing provided with a window or windows 28 slightly smaller than the conducting coating so as to overlap the outline of said coating. Over the window or windows is then placed or wrapped a layer of tin foil 29 or the like to enclose the condenser except for the projecting tongue member 30 thereof, the foil being pressed inwardly through the corresponding window so as to aiorda contact to the conducting coating 26.

The novel condenser herein set forth has been found capable of withstanding applied voltages of the order of magnitude of 100 volts with a dielectric or insulating layer, as the layer 16, of an order of magnitude of only 104 mm.; and a very compact and effective device is thereby afforded, it being found possible to construct condensers of this type of a capacity as high 'as 0.02 mfds. per cm2. while the total thickness of the conimercial condenser need not be over 1 mm. and may be substantially less, depending upon the materials utilized. Through the contacts or terminals provided as aforesaid, a number of the novel condenser units may be interconnected in parallel or series relationship, 'or both, and in manner well understood, to provide for various combinations of capacities and voltages required. While the dielectric insulates, of course, in either direction of current flow, itihas been found preferable to connect the positive potential to the aluminum or underlying base element of the condenser in the case of the application of direct current thereto.

I claim:

1. An electrical condenser, comprising an integral body of strata of aluminum, aluminum oxide, and a superposed coating of a relatively more conducting solid than said intermediate oxide layer and in inactive chemical relationship with the remaining stra-ta.

2. An electrical condenser, comprising an integral lbody of strata of aluminum, aluminum oxide, and a stratumincluding copper.

3. An electrical condenser, comprising an integral body of lstrata of aluminum, aluminum oxide, and a stratum including copper and a copper compound.

4. An electrical condenser, comprising an coating of silver and a metal foil about the latter affording contact means thereto.

6. An electrical condenser, comprising 4a strip of aluminum having a projecting contact lug and its remaining surface being coated with an integral layer 'of aluminum oxide of minute thickness, an intergral coating of copper thereof, an integral overlying coating of silver, a cover of metal foil about the latter affordin a second contact, and means insulating said foil from the said contact lug.

7. A non-rectifying electrical condenser, comprising a metal foil, a dielectric coating consisting of a compound of said foil over one facethereof, molecularly associated therewith and of a thickness of the order of magnitude of 10" mm., and a conductor layer over said dielectric coating and in molecular contact therewith and in inactive chemical relationships with the said metal foil and dielectric coating.

8. A non-rectif ing electrical condenser, comprising a flexi le metal foil, a dielectric coating consistingof a compound of said foil over one face thereof, molecularly associated therewith and of a thickness of the order of magnitude of 10* mm., and a conducting layer over said dielectric coating and in molecular contact therewith and in inactive chemical relationship with the said metal foil and dielectric coating.

9. A non-rectif ing electrical condenser, comprising a flexible metal foil, a dielectric coating consisting of a compound of said foil over one face thereof, molecularly associated therewith and of axthickness of the order of magnitude of 10" min., and a metallic layer over said dielectric coating and in molecular contact therewith and in inactive chemical relationship with the said metal foil and dielectric coating.

10. An electrical device embodying thi-ee molecularly associated layers, the two outer layers being conductive and iii inactive cheniical relationship to each other, one of said layers consisting of a filming metal`v and an intermediate dielectric layer .consisting of a compound of said filming metal.

11. An electrical device embodying three molecularly associated layers, thc'two outer layers being conductive and in inactive cheniical relationship to each other, one of said layers consisting of a filming metal, an intermediate dielectric layer consisting of a' compound of said filming metal, and an additional and more conductive layer over the layer opposite the filming metal layer.

12. An electrical device embodying three molecularly associated layers, the two outer layers being conductive and in inactive chemical relationship to each other, one of said layers consisting of a filming metal, an intermediate dielectric layer consisting of a compound of said filming metal, and an additional and more conductive layer over the layer opposite the filming metal layer and molecularl associated therewith.

13. An electrical evice embodying three molecularly associated layers, the two outer layers being'condiictive and in inactive chemical relationship to each other, one of said layers consisting of a filming metal, and an intermediate dielectric layer consistin of a. compound of said filming metal of su tantially uniform thickness.

14. An electrical device embodying three molecularly associated layers, the two outer layers being'conducfive and in inactive chemical relationship to each other, one of said layers consisting of a filming metal, and an intermediate dielectric layer consisting of a compound of said filmin metal, and of the order of magnitude o 10" mm.

15. An electrical device embodying an integral strip of two strata of conducting solid material in inactive chemical relationship to each other and' one of which is of a filming ty meal, an intermediate dielectric consisting of a compound of said filming type metal stratum and of substantiall uniform thickness and in inactive chemica relationship with the outer layer other than the filmforming layer, and a metal foil about one of the said strata of conducting solid materials affording contact means thereto.

16. An electrical device embodying an integral strip of two strata of conducting solid.

material in inactive chemical relationship to each other and one of which is of a filming type metal and one of which also has a projecting contact lug, an intermediate dielectric consisting of a compound of said filming t-ype metal stratum and of substantially uniform thickness and in inactive chemical relationship with the outer layer other than the film-forming layer, and a metal foil about thel other of the said strata of conducting solid materials affording contact means thereto.

In testimony whereof I afiix my signature.'

` JULIUS EDGAR LILIENFELD. 

